1. Field of the Invention
This invention relates to a process for preparing androst-4-ene 17.beta.-carboxylic acids. More particularly, it relates to a process for preparing androst-4-ene 17.beta.-carboxylic acid by reacting a 21-hydroxy (or a 21-ester) pregn-4-ene-3,20-dione with an inorganic base such as potassium carbonate in an oxygenated hydrocarbon solvent such as methanol in the presence of oxygen to form the desired androst-4-ene 17.beta.-carboxylic acid.
2. Prior Art
It is known that 3-oxoandrost-4-ene 17.beta.-carboxylic acids can be prepared by treating a 3,20-diketopregn-4-ene with sodium hypobromite in a suitable solvent. See, for example, U.S. Pat. No. 2,769,822 to Gash of Monsanto. It is also known that an ester can be hydrolysed to an acid by refluxing with methanol and potassium carbonate under nitrogen.
Surprisingly, it has now been discovered that a 21-hydroxy-20-ketopregn-4-ene or a 21-ester-20-ketopregn-4-ene can be converted to the corresponding androst-4-ene 17.beta.-carboxylic acid by reacting the 20-ketopregn-4-ene with a suitable inorganic base such as potassium carbonate in an oxygenated hydrocarbon solvent such as methanol in the presence of oxygen at low temperatures.